228 INTERNAL SECRETION 



Langley were inclined to adopt this view, chiefly on account of 

 the fact, so frequently illustrated, that the action of adrenalin is 

 unaffected by so-called degenerative resection of the sympathetic 

 nerves that is to say, in cases where degeneration of the resected 

 nerve has already taken place. On the other hand, the experi- 

 ments of Brodie and Dixon show that, \vhere the sympathetic 

 nerve endings are paralysed by apocodein, adrenalin is inactive, 

 in spite of the fact that the muscles have retained their contract- 

 ility, as shown by the effect of agents, such as barium chloride, 

 which have a direct action upon the musculature. It is hardly 

 possible to imagine a chemical destruction of adrenalin by 

 apocodein, hence the only assumption open to us is, that apocodein 

 suppresses those portions of the tissue which, under normal con- 

 ditions, react to the influence of adrenalin. 



Dixon and Brodie localized the seat of action of adrenalin in 

 the sympathetic nerve-terminals. These they defined as " con- 

 necting links between muscle and nerve, which do not, however, 

 form a component part of either the muscular or the nervous 

 fibres." They assume, moreover, that after resection of the 

 nerves, this " neuro-muscular junctional tissue " does not undergo 

 degeneration ; and that this explains the constancy of the effects 

 of adrenalin after degenerative resection of the nerves. 



The histological evidence in favour of this theory is to be 

 found in a discovery described by Fletcher (1897). By intra vitam 

 staining with methylene blue, he discovered a nervous network 

 in the retractor muscle of the penis of the rat, which does not 

 undergo degeneration after resection of either the motor or 

 the inhibitory nerve supplying it, but which does disappear after 

 resection of both. If such a peripheral network were present in 

 all involuntary muscles with a double innervation, the constancy 

 of the action of adrenalin after degenerative resection of the 

 sympathetic would be explained by the fact of this network 

 remaining intact. 



Elliott next investigated the manner in which different muscles 

 react to adrenalin after : first, denervation (degenerative resection 

 of the post-ganglionary sympathetic nerves) ; and second, 

 decentralization (degenerative resection of the preganglionary 

 sympathetic nerves). He found that he was unable to provoke 

 contraction by electric stimulus of a denervated portion of the 

 retractor of the penis of the dog, but that adrenalin was more 

 active upon such muscle than upon that portion in which the 

 innervation \vas normal. After decentralization and denervation, 

 stimulus of the hypogastric and pelvic nerves produced no effect 

 upon the urinary bladder of cats, though relaxation of the bladder 

 and constriction of the urethra were obtainable by means of 

 adrenalin. After removal of the superior cervical ganglion and 

 the ciliary ganglion, together with the ciliary nerves, the instilla- 

 tion or intravenous injection of adrenalin provoked dilation of the 



